Microcapsules adapted to rupture in a magnetic field

ABSTRACT

Controlled release of one or more agricultural chemicals is provided by microcapsules adapted to rupture in a magnetic field. The microcapsules, which may be applied to soil, seeds and/or plants, each have a shell that encapsulates an agricultural chemical, such as a fertilizer, herbicide or insecticide. One or more organosilane-coated magnetic nanoparticles is/are covalently bound into the shell of each microcapsule. For example, (3-aminopropyl)trimethylsilane-coated magnetite nanoparticles may be incorporated into the shell of a urea-formaldehyde (UF) microcapsule during in situ polymerization. In one embodiment, microcapsules encapsulating a fertilizer are applied during seed planting. Controlled release is subsequently triggered after an appropriate period of dormancy by positioning a magnetic field generating device proximate the microcapsules to generate a magnetic field sufficient to rupture the microcapsule shells through magnetic stimulation of the organosilane-coated magnetic nanoparticles. The ruptured microcapsule shells release the fertilizer.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional application of pending U.S.patent application Ser. No. 13/283,734 (docket no. ROC920110138US1),filed Oct. 28, 2011, entitled “MICROCAPSULES ADAPTED TO RUPTURE IN AMAGNETIC FIELD”, which is hereby incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates in general to the production and use offormulations for the controlled release of agricultural chemicals. Moreparticularly, the present invention relates to the production and use ofmicrocapsules adapted to rupture in a magnetic field for the controlledrelease of agricultural chemicals.

2. Background Art

In recent years, considerable effort has been expended to coatfertilizers, pesticides and other agricultural chemicals with polymercoatings which will permit a controlled release of the material uponapplication to plants, soil or the like in a field environment. Theshift to polymer-coated agricultural chemicals is driven by myriadreasons, including material handling safety, ecological concerns andeconomics.

While conventional polymer-coated agricultural chemicals permit acontrolled release of the material upon application, the releasetypically begins at the time of application. Once a conventionalpolymer-coated agricultural chemical is applied, the start of release issubstantially immediate and cannot be altered. Moreover, the releasetypically occurs everywhere within an application zone where aconventional polymer-coated agricultural chemical is appliedirrespective of whether or not the release is desired at a particularlocation within the application zone.

SUMMARY OF THE INVENTION

According to some embodiments of the present invention, microcapsulesadapted to rupture in a magnetic field provide controlled release ofagricultural chemicals. The microcapsules, which may be applied to soil,seeds and/or plants, each have a shell that encapsulates an agriculturalchemical, such as a fertilizer, herbicide or insecticide. One or moreorganosilane-coated magnetic nanoparticles is/are covalently bound intothe shell of each microcapsule. For example,(3-aminopropyl)trimethylsilane-coated magnetite nanoparticles may beincorporated into the shell of a urea-formaldehyde (UF) microcapsuleduring in situ polymerization. In one embodiment, microcapsulesencapsulating a fertilizer are applied during seed planting. Controlledrelease is subsequently triggered after an appropriate period ofdormancy by positioning a magnetic field generating device proximate themicrocapsules to generate a magnetic field sufficient to rupture themicrocapsule shells through magnetic stimulation of theorganosilane-coated magnetic nanoparticles. The ruptured microcapsuleshells release the fertilizer. The controlled release may occur at oneor more selected locations within an application zone based on thepositioning of the magnetic field generated by the magnetic fieldgenerating device. Hence, the farmer can control where and when thereleased occurs.

The foregoing and other features and advantages of the present inventionwill be apparent from the following more particular description of someembodiments of the present invention, as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred exemplary embodiments of the present invention willhereinafter be described in conjunction with the appended drawings,where like designations denote like elements.

FIG. 1 is a cross-sectional view of an enhanced seed coated withmicrocapsules adapted to rupture in a magnetic field for controlledrelease of one or more agricultural chemicals in accordance with someembodiments of the present invention.

FIG. 2 is a cross-sectional view of a crop field site that includes theenhanced seed shown in FIG. 1 planted in soil, as well as a magneticfield generating device in accordance with some embodiments of thepresent invention. Once the enhanced seed has germinated and sprouted,as illustrated in the embodiment shown in FIG. 2, the magnetic fieldgenerating device is positioned proximate the enhanced seed to generatea magnetic field sufficient to rupture the microcapsules coating theenhanced seed and, thereby, release one or more agricultural chemicalsin accordance with some embodiments of the present invention.

FIG. 3 is a cross-sectional view of a crop field site that includes aconventional seed planted in soil and microcapsules adapted to rupturein a magnetic field and applied to the soil, as well as a magnetic fieldgenerating device in accordance with some embodiments of the presentinvention. Once the conventional seed has germinated and sprouted, asillustrated in the embodiment shown in FIG. 3, the magnetic fieldgenerating device is positioned proximate the microcapsules to generatea magnetic field sufficient to rupture the microcapsules and, thereby,release one or more agricultural chemicals in accordance with someembodiments of the present invention.

FIG. 4 is a flow diagram illustrating a method of preparingmicrocapsules adapted to rupture in a magnetic field for controlledrelease of one or more agricultural chemicals in accordance with someembodiments of the present invention.

FIG. 5 is a flow diagram illustrating a method of preparingorganosilane-coated magnetic nanoparticles in accordance with someembodiments of the present invention.

FIG. 6 is a flow diagram illustrating a method of incorporatingorganosilane-coated magnetic nanoparticles into shells of microcapsulesfor controlled release of one or more agricultural chemicals inaccordance with some embodiments of the present invention.

FIG. 7 is a flow diagram illustrating a method of preparing an enhancedseed in accordance with some embodiments of the present invention.

FIG. 8 is a flow diagram illustrating a method of triggering controlledrelease of one or more agricultural chemicals from microcapsules adaptedto rupture in a magnetic field in accordance with some embodiments ofthe present invention.

FIG. 9 is a plan view illustrating a row crop and a farm implementapparatus for use with microcapsules adapted to rupture in a magneticfield for controlled release of one or more agricultural chemicals inaccordance with some embodiments of the present invention.

DETAILED DESCRIPTION

According to some embodiments of the present invention, microcapsulesadapted to rupture in a magnetic field provide controlled release ofagricultural chemicals. The microcapsules, which may be applied to soil,seeds and/or plants, each have a shell that encapsulates an agriculturalchemical, such as a fertilizer, herbicide or insecticide. One or moreorganosilane-coated magnetic nanoparticles is/are covalently bound intothe shell of each microcapsule. For example,(3-aminopropyl)trimethylsilane-coated magnetite nanoparticles may beincorporated into the shell of a urea-formaldehyde (UF) microcapsuleduring in situ polymerization. In one embodiment, microcapsulesencapsulating a fertilizer are applied during seed planting. Controlledrelease is subsequently triggered after an appropriate period ofdormancy by positioning a magnetic field generating device proximate themicrocapsules to generate a magnetic field sufficient to rupture themicrocapsule shells through magnetic stimulation of theorganosilane-coated magnetic nanoparticles. The ruptured microcapsuleshells release the fertilizer. The controlled release may occur at oneor more selected locations within an application zone based on thepositioning of the magnetic field generated by the magnetic fieldgenerating device. Hence, the farmer can control where and when releaseoccurs.

The seeds and plants with which the microcapsules in accordance withsome embodiments of the present invention are useful can be of anyspecies. However, they are preferably plant species that areagronomically important. Of particular importance are barley,canola/rapeseed, corn, cotton, crucifers, curcubits, oats, peanut,potato, rice, rye, sorghum, soybean, sugar beet, sugarcane, sunflower,tobacco, tomato, wheat, as well as other vegetable and leaf crops.

The microcapsules in accordance with some embodiments of the presentinvention can be applied to seeds, soils and/or plants in the form of asuspension; emulsion; slurry of particles in an aqueous medium (e.g.,water); wettable powder; wettable granules (dry flowable); and drygranules. Optionally, the microcapsules in accordance with someembodiments of the present invention may be of differing types (e.g.,having different payload types and/or having different microcapsulecharacteristics so as to rupture at different magnetic field strengths)that can be mixed together and then applied to seeds, soil and/or plantsin one of the forms described above. This option makes it possible torelease different agricultural chemicals at different points in time,release the same agricultural chemicals at different points in time, orto release different agricultural chemicals at the same point in time.

In general, the “one or more agricultural chemicals” encapsulated withinthe microcapsules may include one or more fertilizers, pesticides (e.g.,herbicides, insecticides, fungicides, rodenticides, and biocides), othercrop protection agents (CPAs), and combinations thereof. Preferably, the“one or more agricultural chemicals” encapsulated within themicrocapsules include at least one fertilizer and/or at least oneherbicide.

As utilized herein a “fertilizer” is any organic or inorganic materialof natural or synthetic origin that is conventionally added to soil,seeds, and/or plants to supply one or more plant nutrients. In general,fertilizers typically supply one or more macronutrients and/or one ormore micronutrients. Macronutrients include, for example, nitrogen (N),phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur(S). Micronutrients include, for example, boron (B), chlorine (Cl),copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn).

Organic fertilizers are composed of organic material (plant or animal).Examples of commercially available organic fertilizers include, but arenot limited to, manure, worm castings, compost, and seaweed.

Inorganic fertilizers are composed of inorganic material, such assynthetic chemicals and/or minerals. Examples of commercially availableinorganic fertilizers include, but are not limited to, N-sourcefertilizers such as anhydrous ammonia, urea-ammonium nitrate (UAN),urea, ammonium nitrate, ammonium sulfate, sodium nitrate, and calciumcyanamide; P-source fertilizers such as ammonium phosphates (e.g.,mono-ammonium phosphate (MAP), di-ammonium phosphate (DAP), and ammoniumpolyphosphate (APP)), triple (concentrated) superphosphate, normal(ordinary) superphosphate, phosphoric acid, and pulverized phosphaterock; K-source fertilizers such as potassium chloride, potassiumsulfate, and potassium magnesium sulfate; and mixed fertilizers (alsoreferred to as compound fertilizers) such as granular homogeneous NPKfertilizers, NPK fertilizers containing significant amounts of secondaryand micronutrients, bulk blends containing prescription mixtures of NPKand other essential nutrients formulated for specific geographic areas,and liquid mixed fertilizers (fluid mixes of NP, NS, KS, NPK, NPKS, andthe like).

As utilized herein a “pesticide” is a substance or mixture of substancesintended for preventing, destroying, controlling, repelling ormitigating any pest. Pests include any undesired insects, plants, plantpathogens, mollusks, birds, mammals, fish, and microbes. Pesticidesinclude, but are not limited to, herbicides, insecticides, fungicides,rodenticides, and biocides.

As utilized herein an “herbicide” is a type of pesticide used to killunwanted plants, such as weeds, grasses, and the like. Examples ofcommercially available herbicides include, but are not limited to,phenoxy herbicides such as 2,4-Dichlorophenoxyacetic acid (2,4-D),glyphosate, and triazines such as atrazine. 2,4-D is the most widelyused herbicide in the world. Glyphosate (N-(phosphonomethyl)glycine) isthe most widely used herbicide in the United States.

In modern agriculture, it is generally desirable to apply controlledquantities of nutrients to fields in order to enhance crop quality andyield. Nutrient-rich fertilizers are typically applied at the field'ssurface, where the fertilizer is absorbed into the soil, and someportion of the fertilizer reaches the crop's root system to supportgrowth. This is not an efficient technique for distributing nutrientsbecause the soil itself prevents the delivery of a large portion of thenutrients to the roots. This in turn results in larger or more potentfertilizer applications, ultimately increasing environmental damage dueto run-off and groundwater pollution. Therefore, there exists a need foran enhanced mechanism to deliver nutrients directly to the root systemwithout so much reliance on the soil as the delivery vehicle.

Myriad controlled-release nutrient products exist on the market. Ingeneral, conventional controlled-release nutrient products allow thenutrients to begin releasing the fertilizer directly upon application,followed by a small, steady release until exhaustion of the fertilizer.Unfortunately, this is also an inefficient technique for distributingnutrients. Because conventional controlled-release nutrient products aretypically applied with crop seeds, conventional controlled-releasenutrient products typically begin releasing nutrients before the seedshave begun to germinate, resulting in lost fertilizer.

In accordance with some embodiments of the present invention, theseshortfalls of the prior art (i.e., reliance on soils as the deliveryvehicle and nutrient waste due to premature release) are overcome byproviding an enhanced mechanism that allows one or more nutrients in acontrolled release formulation to be applied during seed planting, andthen allows a full release of the nutrients to be triggered after aperiod of dormancy. For example, some embodiments of the presentinvention incorporate magnetic nanoparticles into the shell of aurethane-based microcapsule with a nutrient payload at the microcapsulecore. The microcapsules may be applied with the crop being planted, forexample, resulting in nutrient-loaded microcapsules being in closeproximity to each seed. Such an embodiment is illustrated in FIG. 3, andan exemplary apparatus for its application and trigger is illustrated inFIG. 9. After a dormant period, the nutrient payload may be releasedunder application of an external magnetic field, which ruptures themicrocapsule shell. In this way, the nutrients may be delivered in fullto each individual seed. This enhanced mechanism reduces the amount ofnutrients applied and reduces nutrient waste, resulting in cost savingsand improved crop performance.

Also, insecticides and herbicides (e.g., phenoxy herbicides used forbroad-leaf weed control) exist on the market that can cause unwanteddamage to certain crops located in drift areas (e.g., a crop rowadjacent to where the insecticide or herbicide is applied). Soybeans,potatoes, and other vegetable crops are particularly susceptible to suchdamage. Therefore, there exists a need to mitigate drift-area cropdamage when utilizing insecticides and/or herbicides, for instance, whentreating the areas between crop rows for pests and weeds withoutaffecting the crops themselves.

In accordance with some embodiments of the present invention, drift-areacrop damage is mitigated by providing an enhanced mechanism that allowsone or more insecticides and/or herbicides in a controlled releaseformulation to be precisely applied and easily triggered. For example,some embodiments of the present invention incorporate magneticnanoparticles into the shell of a urethane-based microcapsule with aninsecticide payload and/or an herbicide payload at the microcapsulecore. The microcapsules are designed to respond to an external magneticfield trigger and rupture. The microcapsules may be applied to the areasbetween the crop rows, for example, during the planting of the crop(e.g., via a liquid dispersal device attached to a conventional planter)and triggered at a later time with a suitable magnetic field. Anexemplary apparatus for application and trigger of such an embodiment isillustrated in FIG. 9. In this manner, the volume of insecticide and/orherbicide applied may be reduced, resulting in both cost savings and asmaller environmental impact. In an alternative embodiment, themicrocapsules may be broadly applied and then precision triggeredbetween the crop rows. This alternative embodiment permits use of aconventional application technology.

Also, an enhanced seed coated with microcapsules in accordance with someembodiments of the present invention can be instructed to release one ormore agricultural chemicals (e.g., fertilizers, herbicides,insecticides, and combinations thereof) on demand. For example, byincorporating magnetic nanoparticles into the shell of a urethane-basedmicrocapsule, encapsulating one or more agricultural chemicals in thecore of the microcapsule, and coating a seed with such microcapsules inaccordance with some embodiments of the present invention, theagricultural chemicals can be released from the microcapsules underapplication of an external magnetic field (i.e., “on demand”). Such anembodiment is illustrated in FIGS. 1 and 2, and an exemplary apparatusfor its application and trigger is illustrated in FIG. 9. Application ofthe magnetic field ruptures the microcapsule shell, which in turnreleases the agricultural chemicals.

In accordance with some embodiments of the present invention,microcapsules adapted to rupture in a magnetic field for controlledrelease of one or more agricultural chemicals are prepared utilizing amulti-step process. This multi-step process is illustrated in FIG. 4.Initially, organosilane-coated magnetic nanoparticles are provided. Thisinitial step corresponds to step 405 in FIG. 4, an example of which isillustrated in greater detail in FIG. 5. Then, the organosilane-coatedmagnetic nanoparticles are incorporated into shells of microcapsuleswhile encapsulating one or more agricultural chemicals. This subsequentstep corresponds to step 410 in FIG. 4, an example of which isillustrated in greater detail in FIG. 6.

In accordance with some embodiments of the present invention, an organotrialkoxysilane, such as aminopropyltriethoxysilane, is reacted with amild acid (e.g., acetic acid, hydrochloric acid, formic acid) in anaqueous solution to form a hydrolyzed silane. This step, whichcorresponds to step 505 in FIG. 5, may be performed at ambienttemperature or elevated temperatures to increase the reaction kineticsof the silane formation. Additionally, the solvent used in this step maybe, for example, tetrahydrofuran, ethanol or methanol. Once the silaneis formed, magnetic nanoparticles are added to the solution and mixed.This step corresponds to step 510 in FIG. 5. The magnetic nanoparticlesmay be, for example, Fe₃O₄ (also referred to as “magnetite”) preparedusing conventional techniques known to those skilled in the art.

An outline of an example of this subsequent step (corresponding to step510 in FIG. 5) is set forth in Equation 1 below.

This then results in the functionalization of a magnetic nanoparticle,which can be then covalently bound into the shell of a urea-formaldehyde(UF) microcapsule while encapsulating one or more agriculturalchemicals. This subsequent step corresponds to step 410 in FIG. 4, whichstep is illustrated in greater detail in FIG. 6. One or moreagricultural chemicals can be incorporated into the core of thesemicrocapsules through conventional microcapsule fabrication processes(e.g., in situ polymerization of a urea-formaldehyde (UF) microcapsuleshell around a core material to encapsulate that material) known tothose skilled in the art.

Also, in accordance with some embodiments of the present invention, anenhanced seed may be prepared by coating microcapsules adapted torupture in a magnetic field for controlled release of one or moreagricultural chemicals (e.g., prepared by the multi-step processillustrated in FIG. 4) onto a conventional seed. This corresponds to themethod illustrated in FIG. 7.

Still further, in accordance with some embodiments of the presentinvention, a controlled release of one or more agricultural chemicalsfrom an enhanced seed coated with microcapsules adapted to rupture in amagnetic field (e.g., prepared by the process illustrated in FIG. 7) maybe triggered by applying a magnetic field to the enhanced seed.Application of a sufficiently strong magnetic field (e.g., 2.5 kA/m or31 Oe) causes magnetic particles covalently bound into the shell of themicrocapsules to rotate at an accelerated rate, thereby rupturing theouter shell of the microcapsules and, in turn, releasing theagricultural chemical.

FIG. 1 is a cross-sectional view of an enhanced seed 100 coated withmicrocapsules 125 adapted to rupture in a magnetic field for controlledrelease of one or more agricultural chemicals in accordance with someembodiments of the present invention.

For example, the enhanced seed 100 may be prepared in accordance withsome embodiments of the present invention by coating a conventional cropseed 120 with microcapsules 125 adapted to rupture in a magnetic fieldfor controlled release of one or more agricultural chemicals. The cropseed 120 (prior to modification by coating with the microcapsules 125 inaccordance with some embodiments of the present invention, as describedbelow with reference to FIG. 7) is conventional. The crop seed 120 maybe selected from any number of commercially available seed products,including “treated” seeds. For example, commercially available seedproducts that are suitable for use as the crop seed 120 include, but arenot limited to corn, cotton, soybean, and wheat.

The microcapsules 125 can be applied “neat” to each conventional cropseed 120, that is without diluting or additional components present.However, the microcapsules 125 are typically applied to eachconventional crop seed 120 in the form of a coating 122 that may containone or more other desirable components including, but not limited to,liquid diluents, binders, fillers for protecting the seeds from stressconditions, and other ingredients to improve flexibility, adhesionand/or spreadability of the coating 122. In some situations, it may bedesirable to add drying agents such as calcium carbonate, kaolin orbentonite clay, perlite, diatomaceous earth or any other adsorbentmaterial. Use of such components in seed treatments is known in the art.See, e.g., U.S. Pat. Nos. 5,876,739 and 6,858,634 B2, which are herebyincorporated herein by reference in their entirety.

Each microcapsule 125 has a shell 126 into which one or moreorganosilane-coated magnetic nanoparticles 127 is/are covalently bound.The shell 126 of each microcapsule 125 defines a core 128 within whichone or more agricultural chemicals 129 is/are encapsulated. In FIG. 1,the core 128 of each microcapsule 125 is illustrated with cross-hatchedlines to denote the core 128 is filled with one or more agriculturalchemicals 129 (and, optionally, one or more solvents, discussed below).In accordance with some embodiments of the present invention, eachmicrocapsule 125 is a urea-formaldehyde (UF) microcapsule having aUF-based shell 126 into which one or more(3-aminopropyl)trimethylsilane-coated magnetic nanoparticles 127 is/arecovalently bound. The UF microcapsule 125 encapsulates one or moreagricultural chemicals 129.

In some embodiments of the present invention, the UF microcapsule 125encapsulates a core solution comprising one or more solvents into whichone or more agricultural chemicals is/are dissolved. The one or moresolvents may be selected from any number of materials that dissolve theone or more agricultural chemicals. Suitable solvents include, but arenot limited to, toluene, ethyl acetate, xylene, acetone, or suitablecombinations thereof.

More generally, suitable solvents include, but are not limited to,aromatic hydrocarbons such as xylenes, naphthalenes, or mixtures ofaromatics; aliphatic or cycloaliphatic hydrocarbons such as hexane,heptane, and cyclohexane; alkyl esters including alkyl acetates andalkyl phthalates; ketones such as cyclohexanone or acetophenone;chlorinated hydrocarbons; vegetable oils; or mixtures of two or moresuch solvents.

While the microcapsules 125 in the example above are described in thecontext of urea-formaldehyde (UF) microcapsules having UF-based shells126, this particular microcapsule material is merely exemplary. Suitablematerials for the shells of the microspheres include, but are notlimited to, urea-formaldehyde, vinylidene chloride-acrylonitrilecopolymer, polyvinyl alcohol, polyvinyl butyral, polymethylmethacrylate,polyacrylonitrile, polyvinylidene chloride, polysulfone, and the like.The one or more agricultural chemicals 129 is/are encapsulated withinthe shells 126 to form microcapsules 125 using techniques known to thoseskilled in the art, such as an in-situ polymerization method, acoacervation method, or an interfacial polymerization method—theseconventional techniques, however, are modified in accordance with thepreferred embodiment of the present invention so that one or moreorganosilane-coated magnetic nanoparticles 127 is/are covalently boundinto the shell 126 of each microcapsule 125. For example, as describedbelow with reference to FIG. 6, the microcapsules 125 may be produced byin situ polymerization of urea-formaldehyde shells 126 around the one ormore agricultural chemicals 129.

FIG. 2 is a cross-sectional view of a crop field site 200 that includesthe enhanced seed 100 shown in FIG. 1 planted in soil 202, as well as amagnetic field generating device 205 in accordance with some embodimentsof the present invention. At a suitable time, for example, after theenhanced seed 100 has germinated and sprouted, as illustrated in theembodiment shown in FIG. 2, the magnetic field generating device 205 ispositioned proximate the enhanced seed 100 to generate a magnetic fieldsufficient to rupture the microcapsules (125 in FIG. 1) coating theenhanced seed 100 and, thereby, release one or more agriculturalchemicals in accordance with some embodiments of the present invention.

In the embodiment shown in FIG. 2, as denoted by a root 203 and a sprout204 emerging from the enhanced seed 100, the release is triggered afterthe enhanced seed 100 has germinated and sprouted. This timing isexemplary. The release may be triggered at any suitable time relative tothe planting of the enhanced seed 100, preferably after an appropriateperiod of dormancy. Release of a fertilizer encapsulated in accordancewith some embodiments of the present invention, for example, may betriggered after an appropriate period of dormancy that is selected toreduce nutrient waste. Release of an herbicide or insecticide inaccordance with some embodiments of the present invention, for example,may be triggered after an appropriate period of dormancy that isselected to avoid exposing the seed to what would be a “toxic level” ofthe herbicide or insecticide at an earlier stage of growth.

The magnetic field generated by the magnetic field generating device 205is sufficient to rupture the microcapsule shells (126 in FIG. 1) throughmagnetic stimulation of the organosilane-coated magnetic nanoparticles(127 in FIG. 1). Application of a sufficiently strong high-frequencymagnetic field causes the organosilane-coated magnetic nanoparticlesembedded in the microcapsule shells to rotate and/or vibrate at anaccelerated rate, thereby rupturing the microcapsule shells of themicrocapsules and, in turn, releasing the encapsulated one or moreagricultural chemicals (129 in FIG. 1).

Preferably, the high-frequency magnetic field applied to the enhancedseed 100 by the magnetic field generating device 205 has a frequency ofapproximately 50-100 kHz and a strength of approximately 2.5 kA/m or 31Oe. The one or more agricultural chemicals is/are released from the core(128 in FIG. 1) of each ruptured microcapsule shell.

The magnetic field generating device 205 is conventional, and typicallyincludes a power supply, a functional generator, an amplifier, amulti-loop coil, and a cooling system. Preferably, the temperature ofthe magnetic field generating device 205 is controlled by cyclingcooling water at 25° C. through the cooling system.

FIG. 3 is a cross-sectional view of a crop field site 300 that includesa conventional seed 301 planted in soil 302 and microcapsules 325adapted to rupture in a magnetic field applied to the soil 302, as wellas a magnetic field generating device 305 in accordance with someembodiments of the present invention. The microcapsules 325 applied tothe soil 302 in FIG. 3 (e.g., applied by the farm implement apparatusillustrated in FIG. 9) correspond to the microcapsules 125 coated ontothe seed in FIG. 1. At a suitable time, for example, after theconventional seed 301 has germinated and sprouted, as illustrated in theembodiment shown in FIG. 3, the magnetic field generating device 305 ispositioned proximate the conventional seed 301 to generate a magneticfield sufficient to rupture the microcapsules 325 and, thereby, releaseone or more agricultural chemicals in accordance with some embodimentsof the present invention.

In the embodiment shown in FIG. 3, as denoted by a root 303 and a sprout304 emerging from the conventional seed 301, the release is triggeredafter the conventional seed 301 has germinated and sprouted. This timingis exemplary. The release may be triggered at any suitable time relativeto the planting of the conventional seed 301, preferably after anappropriate period of dormancy. Release of a fertilizer encapsulated inaccordance with some embodiments of the present invention, for example,may be triggered after an appropriate period of dormancy that isselected to reduce nutrient waste. Release of an herbicide orinsecticide in accordance with some embodiments of the presentinvention, for example, may be triggered after an appropriate period ofdormancy that is selected to avoid exposing the seed to what would be a“toxic level” of the herbicide or insecticide at an earlier stage ofgrowth.

The magnetic field generated by the magnetic field generating device 305is sufficient to rupture the microcapsule shells (126 in FIG. 1) throughmagnetic stimulation of the organosilane-coated magnetic nanoparticles(127 in FIG. 1). Application of a sufficiently strong high-frequencymagnetic field causes the organosilane-coated magnetic nanoparticlesembedded in the microcapsule shells to rotate and/or vibrate at anaccelerated rate, thereby rupturing the microcapsule shells of themicrocapsules and, in turn, releasing the encapsulated one or moreagricultural chemicals (129 in FIG. 1).

Preferably, the high-frequency magnetic field applied to theconventional seed 301 by the magnetic field generating device 305 has afrequency of approximately 50-100 kHz and a strength of approximately2.5 kA/m or 31 Oe. The one or more agricultural chemicals is/arereleased from the core (128 in FIG. 1) of each ruptured microcapsuleshell. In FIG. 3, the core of each microcapsule 325 is illustratedwithout cross-hatched lines to denote the core is no longer filled withone or more agricultural chemicals (129 in FIG. 1).

The magnetic field generating device 305 is conventional, and typicallyincludes a power supply, a functional generator, an amplifier, amulti-loop coil, and a cooling system. Preferably, the temperature ofthe magnetic field generating device 305 is controlled by cyclingcooling water at 25° C. through the cooling system.

FIG. 4 is a flow diagram illustrating a method 400 of preparingmicrocapsules adapted to rupture in a magnetic field for controlledrelease of one or more agricultural chemicals in accordance with someembodiments of the present invention. In the method 400, the stepsdiscussed below (steps 405-410) are performed. These steps are set forthin their preferred order. It must be understood, however, that thevarious steps may occur simultaneously.

In accordance with some embodiments of the present invention, the method400 begins by providing organosilane-coated magnetic nanoparticles (step405). An example of this step 405 of providing organosilane-coatedmagnetic nanoparticles is illustrated in greater detail in FIG. 5. Themethod 400 continues by incorporating the organosilane-coated magneticnanoparticles into shells of microcapsules while encapsulating one ormore agricultural chemicals (step 410). An example of this step 410 ofincorporating the organosilane-coated magnetic nanoparticles into shellsof microcapsules while encapsulating one or more agricultural chemicalsis illustrated in greater detail in FIG. 6.

FIG. 5 is a flow diagram illustrating a method 500 of preparingorganosilane-coated magnetic nanoparticles in accordance with someembodiments of present invention. In the method 500, the steps discussedbelow (steps 505-510) are performed. These steps are set forth in theirpreferred order. It must be understood, however, that the various stepsmay occur simultaneously.

In accordance with some embodiments of the present invention, the method500 begins by reacting an organo trialkoxysilane, such asaminopropyltriethoxysilane, with a mild acid (e.g., acetic acid,hydrochloric acid, formic acid) in an aqueous solution to form ahydrolyzed silane (step 505). This step 505 is performed using standardsilane hydrolysis procedures known to those skilled in the art. Thehydrolyzed silane formation step 505 may be performed at ambienttemperature or elevated temperatures to increase the reaction kineticsof the silane formation. Additionally, the aqueous solution used in thehydrolyzed silane formation step 505 includes a suitable solvent, suchas tetrahydrofuran, ethanol or methanol.

One skilled in the art will appreciate that the organo trialkoxysilanereacted in the hydrolyzed silane formation step 505 may be selected froma group of suitable organo trialkoxysilanes including, but not limitedto, amine-terminated trialkoxysilanes, vinyl-terminatedtrialkoxysilanes, and isocyanate-terminated trialkoxysilanes. Examplesof additional suitable organo trialkoxysilanes include:

-   -   Trimethoxy[3-(methylamino)propyl]silane    -   [3-(2-Aminoethylamino)propyl]trimethoxysilane    -   3-(Triethoxysilyl)propyl        isocyanate-(3-Trimethoxysilylpropyl)diethylenetriamine

Once the hydrolyzed silane is formed in the step 505, the method 500continues by adding magnetic nanoparticles to the solution (step 510).Preferably, the hydrolyzed silane solution is mixed while the magneticnanoparticles are added and/or thereafter.

The magnetic nanoparticles may be, for example, Fe₃O₄ (also referred toas “magnetite”) nanoparticles, cobalt ferrite nanoparticles, or othermagnetic nanoparticles known in the art. Preferably, the magneticnanoparticles have a diameter in the range of approximately 6-25 nm

The magnetic nanoparticles are prepared using conventional techniquesknown to those skilled in the art. For example, magnetite nanoparticlesmay be prepared using a conventional technique known as the“coprecipitation method.” See, for example, the discussion of preparingmagnetite nanoparticles using the coprecipitation method in the articleto M. Yamaura et al., “Preparation and characterization of(3-aminopropyl)triethoxysilane-coated magnetite nanoparticles,” Journalof Magnetism and Magnetic Materials, Vol. 279, pages 210-217, 2004,which is hereby incorporated herein by reference in its entirety.

An example of a conventional technique of preparing magnetitenanoparticles follows. This conventional example is based on an exampleset forth in the M. Yamaura et al. article. A 5 mol/l NaOH solution isadded into a mixed solution of 0.25 mol/l ferrous chloride and 0.5 mol/lferric chloride (molar ratio 1:2) until obtaining pH 11 at roomtemperature. The slurry is washed repeatedly with distilled water. Then,the resulting magnetite nanoparticles are magnetically separated fromthe supernatant and redispersed in aqueous solution at least threetimes, until obtaining pH 7. The M. Yamaura et al. article reports thata typical average diameter of the resulting magnetite nanoparticles is12 nm.

Alternatively, the magnetite nanoparticles may be prepared and thencoated with (3-aminopropyl)triethoxysilane using the silanizationreaction set forth in the M. Yamaura et al. article. That is, themagnetite suspension (i.e., the resulting magnetite nanoparticlesredispersed in aqueous solution at least three times, until obtaining pH7, as discussed above) may be heated with glycerol and 40 ml of a 10%water solution of (3-aminopropyl)triethoxysilane (pH 4.0, adjusted withglacial acetic acid) in a water bath for three hours. The silanizationreaction set forth in the M. Yamaura et al. article occurs in two steps.In the first step, the organosilane is placed into an aqueous solutionof an acid that acts as a catalyst. The organosilane is hydrolyzed, anda condensation reaction occurs to form a silane polymer. In thehydrolysis reaction, alkoxide groups (—OC₂H₅) are replaced by hydroxylgroups (—OH) to form reactive silanol groups to produce siloxane bonds(Si—O—Si). Alcohol (C₂H₅OH) and water are produced as by-products ofcondensation. In the second step, the polymer associates with themagnetite crystallites (or surface clusters) forming a covalent bondwith OH groups. Dehydration as well as adsorption of silane polymers tothe metal oxide occurs. In sequence, after magnetic separation, thesilanized magnetite particles may be thoroughly washed with distilledwater and dried, yielding a fine powder. The M. Yamaura et al. articlereports that a typical average diameter of the resulting(3-aminopropyl)triethoxysilane-coated magnetite nanoparticles is 15 nm.

FIG. 6 is a flow diagram illustrating a method 600 of incorporatingorganosilane-coated magnetic nanoparticles into shells of microcapsulesfor controlled release of one or more agricultural chemicals inaccordance with some embodiments of present invention. In the method600, the steps discussed below (steps 605-630) are performed. Thesesteps are set forth in their preferred order. It must be understood,however, that the various steps may occur simultaneously or at othertimes relative to one another. Moreover, those skilled in the art willappreciate that one or more steps may be omitted.

In accordance with some embodiments of the present invention,conventional microcapsule fabrication processes (e.g., in situpolymerization of urea-formaldehyde (UF) microcapsule shells) may bemodified to incorporate the organosilane-coated magnetic nanoparticlesso that the nanoparticles are covalently bound into shells ofmicrocapsules and to encapsulate one or more agricultural chemicals.Such conventional fabrication processes are described in E. N. Brown etal., “In situ poly(urea-formaldehyde) microencapsulation ofdicyclopentadiene,” Journal of Microencapsulation, Vol. 20, No. 6, pages719-730, 2003 and B. J. Blaiszik et al., “Microcapsules filled withreactive solutions for self-healing materials,” Polymer, Vol. 50, pages990-997, 2009, each of which is hereby incorporated herein by referencein its entirety.

The method 600 begins by preparing an aqueous solution by mixing waterand ethylene maleic anhydride (EMA) copolymer, and then agitating theaqueous solution (step 605). For example, 200 ml of deionized water and50 ml of 2.5 wt % aqueous solution of EMA copolymer may be mixed at roomtemperature (20-24° C.) in a 1000 ml beaker. The beaker may be suspendedin a temperature-controlled water bath on a programmable hotplatemonitored with an external temperature probe. The aqueous solution maybe agitated with a digital mixer driving a three-bladed, 63.5 mmdiameter low-shear mixing propeller placed just above the bottom of thebeaker. Preferably, the aqueous solution is agitated at 200-2000 rpm.

Next, the method 600 continues by adding urea, ammonium chloride,resorcinol, and organosilane-coated magnetic nanoparticles to theaqueous solution, and then adjusting the pH (step 610). Preferably, anappropriate amount of organosilane-coated magnetic nanoparticles areadded to the aqueous solution such that urea-formaldehyde (UF)microcapsules are fabricated that have a magnetic nanoparticle contentof approximately 0.5-20 wt %. For example, while the aqueous solution isunder agitation (e.g., at 800 rpm), 5.0 g urea, 0.5 g ammonium chloride,0.5 g resorcinol, and 1.2 g organosilane-coated magnetic nanoparticlesmay be added in the aqueous solution. The pH may then be raised fromapproximately 2.6 to 3.5 by drop-wise addition of sodium hydroxide(NaOH). One or more drops of 1-octanol may be added to eliminate surfacebubbles.

In lieu of, or in addition to, adding organosilane-coated magneticnanoparticles to the aqueous solution during step 610, the nanoparticlesmay be added to the emulsion during step 625. In either case, anappropriate amount of organosilane-coated magnetic nanoparticles areadded such that urea-formaldehyde (UF) microcapsules are fabricated thathave a magnetic nanoparticle content of approximately 0.5-20 wt %.

The method 600 continues by preparing a core formulation containing oneor more agricultural chemicals (step 615). The core formulation may be acore solution or a core powder. For example, a core solution comprisedentirely of one or more agricultural chemicals may be prepared.Alternatively, a core solution may be prepared by dissolving one or moreagricultural chemicals in one or more suitable solvents. Suitablesolvents include, but are not limited to, toluene, ethyl acetate,xylene, acetone, or suitable combinations thereof. In an alternative tothe preparation of a core solution, it may be desirable to prepare thecore formulation as a core powder comprised of a powdered form of one ormore solid agricultural chemicals.

In Example 1 (a fertilizer-payload embodiment), 60 ml of a core solutioncomprised of ammonium polyphosphate 10-34-0 is prepared. Ammoniumpolyphosphate 10-34-0 is a liquid ammonium polyphosphate fertilizercommercially available under the tradename POLY 10 from PotashCorporation of Saskatchewan Inc., Saskatoon, Saskatchewan, Canada. It isnot uncommon to use ammonium polyphosphate 10-34-0 as a pop-upfertilizer applied directly in the seed furrow. Typically, ammoniumpolyphosphate 10-34-0 is applied in pop-up fertilizer applications atrates of 100 lbs/acre. See, for example, the discussion of ammoniumpolyphosphate 10-34-0 and other conventional fertilizers in M. Alley etal., “Pop-up and/or Starter Fertilizers for Corn,” Virginia CooperativeExtension Publication 3002-1438, 2010, which is hereby incorporatedherein by reference in its entirety. Hence with respect to Example 1,the microcapsules formed later in the method 600 (i.e., in step 625,described below) will be applied to seeds, soils and/or plants in theform of a suspension; emulsion; slurry of particles in an aqueous medium(e.g., water); wettable powder; wettable granules (dry flowable); anddry granules, so that ultimately the ammonium polyphosphate 10-34-0fertilizer encapsulated within the microcapsules is applied in the cropfield at a rate of approximately 100 lbs/acre.

Both liquid and solid ammonium polyphosphates [NH₄PO₃]_(n) arecommercially available. In an alternative to the preparation of a coresolution in step 615 (Example 1), it may be desirable to prepare thecore formulation as a core powder comprised of one or more solidammonium polyphosphates in lieu of, or in addition to, ammoniumpolyphosphate 10-34-0. In this way, a crystalline powder of solidammonium polyphosphate may be encapsulated in lieu of, or in additionto, ammonium polyphosphate 10-34-0.

In Example 2 (an herbicide-payload embodiment), 60 g of a core powdercomprised of glyphosate powder is prepared. As mentioned above,glyphosate (N-(phosphonomethyl)glycine) is the most widely usedherbicide in the United States. Glyphosate, which is a white crystallinepowder, is commercially available in solid form from chemical suppliers,such as Sigma-Aldrich, Saint Louis, Mo. Typically, glyphosate is appliedin herbicide applications at different solution strengths (e.g., 120,240, 360, 480 and 680 g active ingredient per liter) at solution ratesof 3-12 liters/hectare. Therefore, at the most common solution strengthof 360 g active ingredient per liter, glyphosate is applied at a rate ofabout 437-1748 g/acre. Hence with respect to Example 2, themicrocapsules formed later in the method 600 (i.e., in step 625,described below) will be applied to seeds, soils and/or plants in theform of a suspension; emulsion; slurry of particles in an aqueous medium(e.g., water); wettable powder; wettable granules (dry flowable); anddry granules, so that ultimately the glyphosate herbicide encapsulatedwithin the microcapsules is applied in the crop field at a rate ofapproximately 437-1748 g/acre.

Glyphosate is marketed in different solution strengths under numeroustradenames. For example, a water-based solution containing glyphosate, asurfactant, and other substances is marketed under the tradename Roundupavailable from Monsanto Company, St. Louis, Mo. In an alternative to thepreparation of a core powder in step 615 (Example 2), it may bedesirable to prepare the core formulation as a core solution comprisedof one or more glyphosate solutions in lieu of, or in addition to,glyphosate powder.

This core formulation preparation step 615 (e.g., Example 1 or 2) may beperformed at any time prior to the emulsion preparation step 620,described below.

Next, the method 600 continues by preparing an emulsion by adding thecore formulation to the aqueous solution (step 620). For example, a slowstream of 60 ml of a core solution (prepared in step 615) may be addedto the aqueous solution (prepared in step 610) to form an emulsion. Theemulsion is allowed to stabilize, preferably for about 10 min.

Then, the method 600 continues by adding an aqueous solution offormaldehyde to the emulsion, and then reacted for 4 hours at 55° C. toform urea-formaldehyde (UF) microcapsules with shells incorporating theorganosilane-coated magnetic nanoparticles and encapsulating one or moreagricultural chemicals (step 625). For example, after stabilization ofthe emulsion (in step 620), 12.7 g of 37 wt % aqueous solution offormaldehyde (this solution is also known as “formalin”) may be added tothe emulsion (prepared in step 620) to obtain a 1:1.9 molar ratio offormaldehyde to urea. The resulting emulsion may be covered and heatedat a rate of 1° C./min to the target temperature of 55° C. After 4 hoursof continuous agitation (e.g., at 800 rpm), the mixer and hot plate maybe switched off. Once cooled to ambient temperature, the suspension ofmicrocapsules may be separated under vacuum with a coarse-fitted filter.

Finally, the method 600 concludes by washing and then drying themicrocapsules (step 630). For example, the microcapsules (prepared instep 625) may be rinsed with deionized water and air dried for 24-48hours. A sieve may be used to aid in the separation of themicrocapsules. Alternatively, the microcapsules may be retained in theemulsion, which may be applied “as-is” to seeds, soils and/or plants.

FIG. 7 is a flow diagram illustrating a method of preparing an enhancedseed in accordance with some embodiments of present invention. In themethod 700, the steps discussed below (steps 705-710) are performed.These steps are set forth in their preferred order. It must beunderstood, however, that the various steps may occur simultaneously orat other times relative to one another. Moreover, those skilled in theart will appreciate that one or more steps may be omitted.

The method 700 begins by providing microcapsules adapted to rupture in amagnetic field for controlled release of one or more agriculturalchemicals (step 705). For example, such microcapsules may be prepared inaccordance to the method 600, described above with reference to FIG. 6.The microcapsule preparation step may be performed any time prior to thecoating step 710, described below.

The method 700 concludes by coating seeds with the microcapsules (step710). The microcapsules can be applied “neat” to each seed, that is,without diluting or additional components present. However, themicrocapsules are typically applied to each seed in the form of acoating that may contain one or more other desirable componentsincluding, but not limited to, liquid diluents, binders, fillers forprotecting the seeds from stress conditions, and other ingredients toimprove flexibility, adhesion and/or spreadability of the coating. Insome situations, it may be desirable to add drying agents such ascalcium carbonate, kaolin or bentonite clay, perlite, diatomaceous earthor any other adsorbent material.

FIG. 8 is a flow diagram illustrating a method 800 of triggeringcontrolled release of one or more agricultural chemicals frommicrocapsules adapted to rupture in a magnetic field in accordance withsome embodiments of the present invention. In the method 800, the stepsdiscussed below (steps 805-810) are performed. These steps are set forthin their preferred order. It must be understood, however, that thevarious steps may occur simultaneously or at other times relative to oneanother. Moreover, those skilled in the art will appreciate that one ormore steps may be omitted.

The method 800 begins by positioning a magnetic field generating deviceproximate microcapsules adapted to rupture in a magnetic field forcontrolled release of one or more agricultural chemicals (step 805). Forexample, the magnetic field generating device 205 (shown in FIG. 2) maybe positioned proximate an enhanced seed 100 (shown in FIGS. 1 and 2).

Then, the method 800 continues by activating the magnetic fieldgenerating device (step 810). For example, activation of the magneticfield generating device may be accomplished by initiating the flow ofelectrical current through the device's multi-loop coil to generate amagnetic field having the desired strength. For example, as aconsequence of activation of the magnetic field generating device, themicrocapsule shells rupture, the ruptured microcapsules release the oneor more agricultural chemicals encapsulated in the microcapsules.

FIG. 9 is a plan view illustrating a row crop 900 and a farm implementapparatus 950 for use with microcapsules adapted to rupture in amagnetic field for controlled release of one or more agriculturalchemicals in accordance with some embodiments of the present invention.

The row crop 900 has a plurality of rows 912 spaced apart from oneanother by row spacing 914. Also shown in FIG. 9 are the areas betweenthe rows 912 of crop 900, such areas being designated area 918. Row crop900 may comprise rows of any crop such as corn, potato, soybean, andwheat, as well as other vegetable and leaf crops. Row spacing 914 may bemeasured from the center 916 of a given row to the center 916 of anadjacent row, for example. Row spacing 914 may be any suitable distancefor the crop. For example, row spacings used in some embodiments of thepresent invention might include 20, 22, 30, 36, 38, and 40 inch rowspacings in order to be compatible with certain existing commerciallyavailable planting, tilling and/or harvesting equipment, although theexact spacing and/or units of measurement can be varied from theexamples without departing from the scope of the invention as claimed.

Typically, the farm implement apparatus 950 is towed behind a tractor(not shown). The farm implement apparatus 950 is typically connected tothe tractor with a draw-bar 952 as illustrated in FIG. 9, or athree-point hitch. In the embodiment illustrated in FIG. 9, the draw-bar952 is attached to a header bar 954, which is attached to eightin-crop-row bars 956 and seven between-crop-row bars 958. Theconfiguration of the farm implement apparatus 950 illustrated in FIG. 9is an exemplary. One skilled in the art will appreciate that farmimplement apparatus having other configurations are possible within thescope of the invention as claimed. For example, the size of the farmimplement apparatus need not be B-rows as illustrated in FIG. 9.

The farm implement apparatus 950 may be, for example, a modified-versionof a conventional planter. An example of a suitable conventional planteris the John Deere MaxEmerge XP Planter, available from Deere andCompany, Moline, Ill.

Conventional planters precisely sow seed along a number of rows, andtypically vary in size from 2-rows to 48-rows. Seeds are distributed byconventional planters through devices referred to as “row units,” whichare spaced evenly across the planter. The space between the row units(typically referred to a “row spacing”) can vary greatly, but typicallythe row spacing is 30 inches. Conventional planters typically have aseed bin for each row, as well as a fertilizer bin for each row. In eachseed bin, plates are installed having a configuration (e.g., number ofteeth and tooth spacing) based on the seed type and the sowing rate. Thesize of the space between the teeth is just large enough to accommodateone seed at a time. Other conventional planters have a large seed binfor seeds that are distributed to each row, in lieu of a seed bin foreach row.

The farm implement apparatus 950 includes a seed bin 962 for each row,as well as a fertilizer bin 964 for each row. The seed bins 962 and thefertilizer bins 964, which are mounted on the in-crop-row bars 956, areconventional. A conventional “row unit” (not shown) underlies each ofthe seed bins 962. Similarly, a conventional dispersal device (notshown) underlies each of the fertilizer bins 964.

In accordance with some embodiments of the present invention, the farmimplement apparatus 950 also includes one or more magnetic fieldgenerating devices (e.g., eight in-crop-row magnetic field generatingdevices 980 and seven between-crop-row magnetic field generating devices985) and one or more herbicide bins (e.g., seven herbicide bins 995).The herbicide bins 995 are mounted on the between-crop-row bars 958. Thein-crop-row magnetic field generating devices 980 are mounted on thein-crop-row bars 956, but the between-crop-row magnetic generatingdevices 985 are mounted on the between-crop-row bars 958. Each of theeight in-crop-row magnetic field generating devices 980 in FIG. 9corresponds to the magnetic field generating device 205 in FIG. 2.Except with respect to their between-crop-row locations, thebetween-crop-row magnetic field generating devices 985 are substantiallyidentical to the in-crop-row magnetic field generating devices 980. Aconventional dispersal device (not shown) underlies each of theherbicide bins 995.

Preferably, the magnetic field generating devices 980 and 985 areconfigured to remain completely above ground. In an alternativeembodiment, however, the magnetic field generating devices 980 and 985may, at least partially, extend below ground (e.g., as probes). Inanother alternative embodiment, one or more of the magnetic fieldgenerating devices 980 and 985 may be stationary (e.g., mounted on polesor buried beneath the soil, especially in an environment such as agreenhouse) in lieu of, or in addition to, being mounted on the farmimplement apparatus 950. In yet another alternative embodiment, one ormore of the magnetic field generating devices 980 and 985 may be mountedon an aircraft in lieu of, or in addition to, being mounted on the farmimplement apparatus 950.

In the embodiment illustrated in FIG. 9, the farm implement apparatus950 is capable of performing several functions (described below) relatedto the use of microcapsules adapted to rupture in a magnetic field forcontrolled release of one or more agricultural chemicals. One skilled inthe art will appreciate, however, that any number of these severalfunctions may be performed individually or in subsets by separate farmimplement apparatus or other apparatus without departing from the scopeof the invention as claimed.

In some embodiments of the present invention, the farm implementapparatus 950 may be used in planting enhanced seeds (100 in FIGS. 1 and2), as well as in subsequently triggering release of one or moreagricultural chemicals from the microcapsules (125 in FIG. 1) coatingthe enhanced seed. For example, the enhanced seeds (i.e., seeds coatedwith microcapsules adapted to rupture in a magnetic field for controlledrelease of the one or more agricultural chemicals, such as a fertilizer)may be loaded into the seed bins 962 of the farm implement apparatus950, which is then towed behind a tractor through a field to plant theenhanced seeds as the row crop 900. If the payload of the microcapsulescoating the enhanced seeds is fertilizer, for example, the fertilizerbins 964 of the farm implement apparatus 950 need not be used. After theenhanced seeds have germinated and sprouted, the farm implementapparatus 950 is again towed behind a tractor through the field whilethe eight in-crop-row magnetic field generating devices 980 areactivated to trigger release of the one or more agricultural chemicals(e.g., fertilizer) from the microcapsules coating the enhanced seed.

In other embodiments of the present invention, the farm implementapparatus 950 may be used in planting conventional seeds (301 in FIG. 3)while simultaneously applying microcapsules (325 in FIG. 3) adapted torupture in a magnetic field for controlled release of one or moreagricultural chemicals, as well as in subsequently triggering release ofthe one or more agricultural chemicals from the microcapsules.

In a first example, the conventional seeds may be loaded into the seedbins 962 and the microcapsules adapted to rupture in a magnetic fieldfor controlled release of the one or more agricultural chemicals (e.g.,a fertilizer) are loaded into the fertilizer bins 964 of the farmimplement apparatus 950, which is then towed behind a tractor through afield to plant the seeds as the row crop 900 while simultaneouslyapplying the microcapsules. After a suitable period of time has passed(e.g., after the conventional seeds have germinated and sprouted), thefarm implement apparatus 950 is again towed behind a tractor through thefield while the eight in-crop-row magnetic field generating devices 980are activated to trigger release of the one or more agriculturalchemicals from the microcapsules.

In a second example, the conventional seeds may be loaded into the seedbins 962 and the microcapsules adapted to rupture in a magnetic fieldfor controlled release of the one or more agricultural chemicals (e.g.,a phenoxy herbicide such as 2,4-Dichlorophenoxyacetic acid (2,4-D)) areloaded into the herbicide bins 995 of the farm implement apparatus 950,which is then towed behind a tractor through a field to plant the seedsas the row crop 900 while simultaneously applying the microcapsules inarea 918 between the rows 912 of crop 900. After a suitable period oftime has passed (e.g., after the conventional seeds have germinated andsprouted), the farm implement apparatus 950 is again towed behind atractor through the field while the seven between-crop-row magneticfield generating devices 985 are activated to trigger “precision”release of the one or more agricultural chemicals from the microcapsulesin area 918 between the rows 912 of crop 900. That is, the boundary ofrelease is precisely controlled to be within area 918 between the rows912 of crop 900 (and, importantly, not in the rows 912 of crop 900 tomitigate drift-area crop damage).

As mentioned above, 2,4-D is the most widely used herbicide in theworld. When it was commercially released in 1946, 2,4-D became the firstsuccessful selective herbicide. It only kills broadleaf plants (alsoknown as “dicots”), leaving behind grasses (also known as “monocots”).Hence, 2,4-D provides effective weed control in wheat, maize (corn),rice, and similar grass crops. Unfortunately, 2,4-D and other phenoxyherbicides can cause unwanted damage to certain crops located in driftareas (e.g., a crop row adjacent to where the herbicide is applied).Soybeans, potatoes, and other vegetable crops are particularlysusceptible to such damage. As a consequence, some crops that have beengenetically engineered to be resistant to 2,4-D. For example,genetically engineered maize (corn) and soybean resistance to 2,4-D hasbeen demonstrated through insertion of a bacterial aryloxyalkanoatedioxygenase gene. Some embodiments of the present invention (e.g., thesecond example, above, and the yet other embodiments, below) provide aneffective alternative to the use of such genetically engineered cropsbecause the herbicide is precisely applied and easily triggered for“precision” release.

In yet other embodiments of the present invention, the farm implementapparatus 950 may be used in precisely triggering release of one or moreagricultural chemicals (e.g., a phenoxy herbicide such as2,4-Dichlorophenoxyacetic acid (2,4-D)) from microcapsules that wereearlier broadly applied (e.g., sprayed via a conventional boom sprayeror aircraft) to the row crop 900. After the microcapsules have beenbroadly applied to the row crop 900, the farm implement apparatus 950 istowed behind a tractor through the field while the sevenbetween-crop-row magnetic field generating devices 985 are activated totrigger “precision” release of the one or more agricultural chemicalsfrom the microcapsules in area 918 between the rows 912 of crop 900.That is, the boundary of release is precisely controlled to be withinarea 918 between the rows 912 of crop 900 (and, importantly, not in therows 912 of crop 900). Because the herbicide is broadly applied andeasily triggered for “precision” release, such embodiments of thepresent invention provide an effective alternative to the use of cropsgenetically engineered to be herbicide resistant.

The precision release feature of some of the embodiments of the presentinvention provides a number of additional advantages. For example, theprecision release feature makes it possible to broadly applyagricultural chemicals but yet mitigate the adverse effect of “drift”onto adjacent fields and other areas of inadvertent application. Also,the precision release feature makes it possible for farmers to useherbicides such as glyphosate (N-(phosphonomethyl)glycine) as apost-emergence herbicide without utilizing crops that have beengenetically engineered to be resistant to such herbicides.Conventionally, the use of glyphosate as a post-emergence herbiciderequires the use of such genetically engineered crops. As mentionedabove, glyphosate is the most widely used herbicide in the UnitedStates. Glyphosate, which is commercially available under the tradenameRoundup from Monsanto Company, St. Louis, Mo., is a broad-spectrumsystemic herbicide used to kill weeds and grasses which commonly competewith crops. Because glyphosate is only effective on actively growingplants, it is not effective as a pre-emergence herbicide. Crops thathave been genetically engineered to be resistant to glyphosate, forexample, are available under the tradename Roundup Ready from MonsantoCompany, St. Louis, Mo. Conventionally, such genetically engineeredcrops are required in order to use glyphosate as a post-emergenceherbicide.

One skilled in the art will appreciate that many variations are possiblewithin the scope of the present invention. For example, although someembodiments of the present invention are described herein in the contextof producing and using formulations for controlled release ofagricultural chemicals in row crops, the present invention may beutilized in the context of producing and using formulations forcontrolled release of one or more agricultural chemicals in other plantsand environments such as greenhouse plants, house plants, trees, shrubs,bushes, grasses, weeds, flowers, and the like. Thus, while the presentinvention has been particularly shown and described with reference tosome embodiments thereof, it will be understood by those skilled in theart that these and other changes in form and detail may be made thereinwithout departing from the spirit and scope of the present invention.

What is claimed is:
 1. A method of preparing an enhanced seed, themethod comprising the steps of: providing microcapsules adapted torupture in a magnetic field for controlled release of one or moreagricultural chemicals, wherein each microcapsule has a shellencapsulating an agricultural chemical and into which one or moreorganosilane-coated magnetic nanoparticles is/are covalently bound,wherein the agricultural chemical is selected from a group of activeingredients consisting of fertilizers, herbicides, insecticides, andcombinations thereof; coating a seed with the microcapsules.
 2. Anenhanced seed, comprising: a seed; microcapsules coating the seed,wherein each microcapsule has a shell encapsulating an agriculturalchemical and into which one or more organosilane-coated magneticnanoparticles is/are covalently bound, wherein the agricultural chemicalis selected from a group of active ingredients consisting offertilizers, herbicides, insecticides, and combinations thereof.
 3. Theenhanced seed as recited in claim 2, wherein the microcapsules includeurea-formaldehyde (UF) microcapsules each having a shell into which oneor more (3-aminopropyl)trimethylsilane-coated magnetite nanoparticlesis/are covalently bound.
 4. The enhanced seed as recited in claim 3,wherein the shell of each UF microcapsule encapsulates at least onefertilizer.
 5. The enhanced seed as recited in claim 3, wherein theshell of each UF microcapsule encapsulates at least one pesticide.